DESCRIPTION: (provided by the applicant) The functional role of the opioid peptides (encephalin and dynorphins) in substance abuse and addiction is well recognized but not fully understood. Advances in this area would be stimulated by information regarding the concentration, lifetime, and regulation of opioid peptides in the extracellular space of the living brain. The goal of this research project is to overcome the technical challenges that now obstruct access to that information. Two technical obstacles must be overcome. First, opioid peptides exist at low levels in the extracellular space. Second, they exist as families of peptides rather than individual, distinct substances. Thus, analytical methods with exceptionally high sensitivity and excellent selectivity are necessary but are not yet widely available. The sensitive and selective methods developed during this project will be built on a platform of state-of-the-art, commercially available chromatographic and mass spectrometric instrumentation. Thus, they will be readily adoptable by the numerous research laboratories addressing the petrochemical aspects of substance abuse. A capillary pipet will be used to collect small, undiluted samples of neat extracellular fluid of striatal tissue slices from rats. The peptide content will be determined in samples acquired under basal conditions, during potassium-induced depolarization, in the absence of calcium ion, and in the presence of peptidase inhibitors.